Rate agile rate-adaptive digital subscriber line

ABSTRACT

Methods and apparatus for maintaining the maximum achievable data rate on a DSL line, up to and including a rate to which a user subscribes is described. Performance monitoring is conducted on the DSL line on an ongoing basis to determine noise margins in each direction. Each noise margin is compared against pre-determined decreasing/increasing thresholds to determine whether the line characteristics dictate a data rate change without loss of synchronization. The invention supports dynamic provisioning changes including application driven service level change requests, e.g., new bandwidth-on demand services. In some embodiments, a combination of existing and new embedded operations channel (EOC) messages are used to implement the modem data rate changes. New EOC messages may be implemented using some of the reserved and/or vendor proprietary Opcodes currently permitted. Modem assigned data rate changes are implemented without a disruption of service, e.g., without the need for re-initialization and/or re-synchronization.

FIELD OF THE INVENTION

The present invention relates generally to the field of communicationssystems and, more particularly, to the field of Digital Subscriber Line(DSL) data rate control.

BACKGROUND OF THE INVENTION

ADSL communications rates are normally established between a customer'smodem and the central office equipment based on initial line conditionsand a subscribed to service rate. This initial line rate normallyremains fixed unless poor line conditions interrupt service orcommunication with the central office is interrupted for some otherreason, e.g., as part of provisioning a new service rate. Anyre-synchronization results in a disruption of service.Re-synchronization due to poor line conditions can result in aratcheting down in the provided line rate over time. To provision ahigher service rate, e.g., in response to a subscriber request for achange in service, a full initialization operation is normally performedwhich disrupts any ongoing communions sessions being conducted over theline. Thus, in current systems, line rates are not changed on-the-flyand a service subscriber must subscribe to a rate which supports themost demanding application used by the subscriber even if the highbandwidth application is used only on a sporadic basis or faceinterruptions in service each time a rate change is made.

Problems with existing DSL will become clear if one appreciates theexisting setup and resynchronization process. In Asymmetric DigitalSubscriber Line (ADSL) systems, a user's modem at a customer site, e.g.an ADSL Termination Unit-Remote (ATU-R), when powered on, attempts toestablish communications with a modem at a central office, e.g. aDigital Subscriber Line Access Multiplexer (DSLAM) Line Port, ADSLTermination Unit-Central office (ATU-C).

Known initialization sequences, used to establish communications betweena central office's DSLAM modem, an ATU-C, and a Customer PremisesEquipment (CPE) modem, an ATU-R, in the ADSL environment are describedbelow. These initialization sequences are sometimes referred to as thetraining-up of the modem or ‘showtime’. The series of events comprisingthe initialization sequence may be initiated due to any of the followingconditions.

-   -   1. The initial power-up of the ATU-R.    -   2. Subsequent power-up or reboot of the ATU-R.    -   3. Loss of power to the ATU-R and subsequent restoration of        power to the ATU-R.    -   4. The initial power-up; reset or re-provision of the ATU-C.    -   5. Loss of sync between the ATU-C and the ATU-R.    -   6. Loss of power to the ATU-C and subsequent restoration of        power to the ATU-C.    -   7. Replacement of the DSLAM Line Card with ATU-C ports and        initialization of the Line Card.

The drawing 100 of FIG. 1 describes a known initialization sequence usedto establish communications, in an ADSL environment, between a centraloffice DSLAM modem ATU-C 102 and a CPE modem ATU-R 104 for the ANSIT1.413 mode of operation. The ADSL initialization signals can bedescribed in terms of frequencies or, equivalently, in terms of the toneindices representing those frequencies, where the frequency of tone k isk*4.3125 kHz. ATU-C 102 is in a quiescent state, C-QUIET 106, monitoringfor an activation signal from ATU-R 104. ATU-R 104 generates an initialactivation request signal, R-ACT-REQ108, defined as the k=8 tone (34.5kHz), sends signal R-RACT-REQ 108 to ATU-C 102, and then enters aquiescent monitoring state, R-QUIET 110. ATU-C 102 receives theR-ACT-REQ 108 signal and generates a response signal, C-ACT 114. TheC-ACT 114 signal is used to select timing modes, and may be one of thefollowing signals: C-ACT1 k=48 tone (207 kHz), C-ACT2 k=44 tone (189.75kHz), C-ACT3 k=52 tone (224.25 kHz), or C-ACT4 k=60 tone (258.75 kHz).ATU-C 102 sends the selected C-ACT 114 signal to ATU-R 104, and enters aquiescent monitoring state, C-QUIET2 116. ATU-R 104 receives C-ACTsignal 114 and generates an acknowledgment signal R-ACK 118. The R-ACK118 signal acknowledges reception of the C-ACT signal 114, and selectssome additional parameters, where R-ACK 118 is one of the followingsignals: R-ACT1: k=10 tone (43.125 kHz) or R-ACT2 k=12 tone (51.76 kHz).ATU-R 104 sends the selected R-ACK signal 118 to ATU-C 102, and thenenters a quiescent monitoring state, R-QUIET2 120. ATU-C 102 receivesthe R-ACT signal 118, generates an acknowledgement signal, C-REVEILLE122, which is the k=56 tone (241.5 kHz) tone, and sends C-REVEILLE 122to the ATU-R 104. ATU-R 104 detects the C-REVEILLE signal 122, waitsuntil C-REVEILLE 122 has finished, and then sends R-REVERB1 signal 124.R-REVERB1 124 is the first signal in the initialization sequence that isnot a single tone. The exact tones (subchannels) used to generateR-REVERB1 124 are vendor discretionary, and may be from 1 to 31. Toensure that the R-REVERB1 signal 124 has the same power spectral density(PSD) mask as the ADSL upstream data, the most common tones begin attone 6 or 7 and end at tone 30 or 31.

A known initialization sequence is used to establish communications inan ADSL environment between a central office DSLAM modem, ATU-C 102, anda CPE modem, ATU-R 104. The G.dmt (G.hs) mode of operation shall now bedescribed. G.hs uses 3-tone redundancy for robustness of ADSL modemtraining. The ATU-R 104 sends tones k=9, 17, 25 to indicate that ATU-R104 can operate in ADSL over POTS (G.dmt Annex A). These three tones(k=9, 17, 25) are known as the A43 upstream carrier set. The ATU-R 104may also send tones k=37, 45, and 53 to indicate that it can communicateG.hs information over these carriers as well. These tones (k=37, 45, 53)are the B43 upstream carrier set. ATU-C 102, which has been monitoringfor a request from ATU-R 104, receives the upstream carrier set(s) andresponds with a downstream carrier set(s) of tones. Tones k=40, 56, 64,which are the A43 downstream carrier set, indicate that ATU-C 102 canoperate in ADSL over POTS. Also, the ATU-C 102 may send tones k=72, 88,96, which are the B43 downstream carrier set, to indicate that it cancommunicate using this carrier set as well.

Modems 102, 104 then communicate, negotiate capabilities, and train thetransceivers using the negotiated parameters. The negotiation ofcapabilities may involve: sending test signals on the DSL line,measuring of Signal-to-Noise-Ratio (SNR) and Attenuation (ATN) at thereceiving end of the line, requesting test parameter updates, obtaininginitial values for maximum possible achievable data rates on the DSLline between modems 102 and 104, transferring initial subscribed datarate information to ATU-C 102 from a provisioning system, calculating aninitial assigned data rate value, and transferring of the assigned datarate value from ATU-C 102 to ATU-R 104.

The ITU G.992.1 G.DMT standard, which may be used by DSLAM modem ATU-C102 and CPE modem ATU-R 104, divides frequencies into 255 sections, orbins. The separation between each bin is 4.3125 KHz. Each bin can carry0 or 2¹⁵ bits, with the resulting possible bit rates in increments of 32Kbps. The downstream data traffic, from Central Office DSLAM Line portmodem ATU-C 102 to the user's CPE modem ATU-R 104 uses bins 37 to 255,or 159.562525 to 1099.6875 KHz. The upstream data traffic, from theuser's CPE modem ATU-R 104 to the Central Office DSLAM modem ATU-C 102,uses bins 6 to 29, or 25.875 to 125.0625 KHz. Noise and otherinterference on the line cause attenuation on the line, which in turndecreases the Signal-to-noise ratio, SNR. During initialization, basedupon provisioning and determined maximum achievable data rate, the modemATU-R is assigned data rates designating which bins may be used for theupstream and downstream directions.

In known systems, once a CPE modem ATU-R 104 is powered on, itperiodically sends out a tone (R-ACT-REQ) 108 in T1.413 and/or multipletones (upstream carrier set(s)) in G.hs, in at attempt to sync to theATU-C 102, as previously described. Once sync has been establishedbetween modems ATU-R 104 and ATU-C 102 and the initial provisioning hascompleted, resulting in an assigned data rate value, the ATU-R 104 maycommunicate with the ATU-C 102 at that initial assigned data rate value.Communications may be interrupted by the following fault or terminationconditions: a power loss at either end, the threshold of the sync marginis negatively impacted, or the SNR falls below an acceptable level,e.g., due to changing line conditions. In any of these fault ortermination scenarios, including the low SNR case, the modem, ATU-R 104will attempt to re-sync with the ATU-C 102, e.g., at a new lower datarate. Unfortunately, the re-synchronization process causes a disruptionof service. If the re-sync was triggered by an unacceptable low SNR,typically the new initial assigned data rate value established duringthe re-initialization process will be lower than the previous data rate.Thus, over extended periods of time, the re-synchronization processoften results in a ratcheting down in terms of the data rate since there-sync process is triggered in response to decreasing line conditionquality but not improvements in SNR. This is understandable since thecurrent process involves disrupting any on-going communications sessionwhen resynchronization is preformed to implement a data rate change.

Thus, in known systems, there is no method today to gracefully decreasethe assigned data rate to adapt to changing line conditions without adisruption in service, i.e., the resynchronization process used at startup is used each time SNR falls to an unacceptable level.

In existing systems, if the line conditions are insufficient duringinitialization, to set the assigned data rate at the subscribed to,e.g., provisioned, data rate, the assigned data rate is set at a lowersupported data rate, and the user is limited to that lower assigned rateas a ceiling data rate for the communications session. With knownsystems, there is no attempt to increase the assigned data rate if theline conditions should improve during operation, and there is no methodtoday to increase the assigned data rate without going through aninitialization sequence which results in a disruption of service.

Users of DSL lines, at different times, require different levels ofservice, e.g., based on the application currently in use. For example auser may primarily use the DSL line for voice and require a relativelylow data rate; however, occasionally, for short intervals, the DSL linemay also be used for video conferencing requiring a relatively high datarate. In order for the user to satisfy his needs, he could continuouslysubscribe to a higher level of service than he generally needs; however,this approach is inefficient since during most of the time, the userwould be wasting bandwidth, e.g., by paying for bandwidth that goesunused. It would be advantageous if service level changes could berequested and implemented on demand, to supply additional bandwidth whenneeded by a specific application and then remove the additionalbandwidth when the application terminates without interfering with otheron-going communications sessions which are terminated in existingsystems.

Based upon the above discussion, it is clear that there is a need tohave a dynamic and seamless adjustment capability for controlling DSLmodem rates without the need to perform a completeinitialization/resynchronization process which would interfere withongoing communications sessions. In particular, there is a need forsupporting downward rate adjustments in the case of a worsening of lineconditions, e.g., before synchronization is lost. There is also a needfor allowing a line rate to be increased in response to improved lineconditions without requiring re-synchronization processes which wouldinterfere with existing communications sessions. In addition, there is aneed for a method which would allow a DSL rate to be changed, e.g., inresponse to changes in a subscriber's services needs, withoutinterrupting existing communications sessions.

SUMMARY OF THE INVENTION

In DSL communication systems, a user subscribes or purchases a serviceplan, specifying a DSL level of service, corresponding to maximum DSLdata rates that the user may be assigned. The provisioning system willretain the provisioned rate information associated with a user forfuture reference. When a user, with a CPE DSL modem, powers on, attemptsto initialize, establish synchronization, and establish communications,the CPE DSL modem performs an initialization sequence, an exchange ofsignaling and information, with a central office DSLAM modem. Theinitialization sequence may involve an initial determination of the linecharacteristics, e.g., line attenuation and SNR, to find out the currentmaximum supported data rate on the DSL line. The supported data rate isthe maximum rate, under the present line conditions that may be usedwhile still maintaining an acceptable SNR corresponding to an acceptablebit error rate during data transmissions. Then, the DSLAM modem, usingthe lower of the provisioned rate and the supported rate as an upperboundary, may assign a data rate to the subscriber. In some embodiments,the line data rate is changed in 32 Kbps increments.

In accordance with the invention, the CPE DSL modem and/or the DSLAMmodem, during normal operation, monitors the line characteristics, e.g.,SNR and ATN on an ongoing, e.g., periodic basis, and determines, as afunction of one or more signal to noise measurements, a noise margin.For each noise margin determined, a comparison may be performed againstpre-determined limits, e.g., a decreasing adjustment threshold, todetermine whether the line quality has degraded, and may, in the nearfuture, no longer support the current assigned data rate, which couldresult in an interruption in service and the need for resynchronization.The decreasing adjustment threshold level can be set at a level thatwill trigger a transition to a lower supportable data rate, before anyinterruption in service occurs, e.g., before interruption of service andfull resynchronization is required. In accordance with the invention,this triggered transition to a lower supportable data rate level may beperformed dynamically during operation, without any interruption inservice, re-initialization, or resynchronization. For each noise margindetermined, a comparison may also be made against pre-determined limits,e.g., an increasing adjustment threshold, to determine whether the linequality has improved enough to support a higher data rate. In such acase where it is determined that the line quality will support a higherdata rate, the line rate may be increased without loss insynchronization and/or interruption of service. The new line rate isnormally less than or equal to the currently subscribed to, e.g.,provisioned, level which is used as an upper limit on the data ratesupplied, line conditions permitting. The assigned data rate level maybe increased by one step level at a time, e.g., in 32 Kbs increments, inaccordance with the invention. The increase in data rate between theDSLAM and CPE DSL modems may be accomplished without an interruption inservice, re-initialization, or re-synchronization, in accordance withthe invention. The methods of the current invention, allow for a user'sassigned data rate to be dynamically and seamlessly varied up or down,tracking the varying line conditions, and providing the user with thehighest achievable data rate, for which the user is provisioned.

The approach, of performance monitoring with ongoing rate adjustments,of the invention, is in sharp contrast, to the known methods of modemrate control, where a subscriber's assigned line rate is set once,during initialization, at the supportable rate at that time, which maybe at or below the subscribed (purchased) provisioned rate and does notchange during operation unless communication is interrupted and aresynchronization process is performed. In the known method, if theinitial assigned rate was set below the provisioned rate, e.g., due topoor initial conditions, the rate will not be adjusted upward and theuser will have to operate at the lower rate even if line conditionsshould improve to the point where a higher data rate could be supported.In the known method, if the line quality drops to no longer support theinitial assigned rate, the CPE DSL modem will lose communications withthe DSLAM modem, and the CPE DSL modem re-initializes andre-synchronizes to re-establish communications at a lower data rate.Thus, in contrast to the known systems which interrupt communicationswith each upward or downward rate change, the present invention supportsrate changes without interfering with ongoing communications sessions.

In accordance with another novel feature of the invention, service levelrequest changes may be processed dynamically during normal operations bythe provisioning system. Service level request changes can becommunicated to the provisioning system from the subscriber over the DSLconnection, e.g., via an Internet connection, and/or anothercommunication path such as a telephone line. Service level changerequests may include long term subscribed provisioning changes and/orshort term or temporary application driven changes. The applicationdriven change requests may include new services to be sold by serviceproviders, e.g., bandwidth-on-demand type services. The service providercould provide the user with temporary high bit rate services, e.g., whenevoked by a request from a specific application, and then terminate thehigh bit rate service, when the application completes. Such services canbe billed on a usage basis instead of a flat rate if desired. Thedynamic service level request changes are forwarded via the provisioningsystem to the DSLAM and/or CPE DSL modem where new subscribed datalevels are installed. Current maximum supportable levels are determined,based on current line conditions. A comparison is made between the newsubscribed rate and the current maximum supported rate, and the assignedrate is adjusted accordingly. If at the time of the service level changerequest, the new subscriber rate, was not supported by the current lineconditions, the new subscribed data rate is still loaded into the DSLAMand/or CPE DSL modems; this allows for future upward ratcheting of theassigned data rate by the performance monitoring routine, should lineconditions permit. This transition of the DSLAM and CPE DSL modems to anew assigned rate is performed without interruption of service,re-initialization, or re-synchronization, in accordance with theinvention.

The data rate change implementation of the present invention may beimplemented through hardware, software, firmware, and/or any combinationthereof in the communications system. Such implementations may includemodifications to the line card in the DSLAM modem such as addingfirmware to allow the line port data rate to be changed “on-the-fly”without the need to re-sync with the remote CPE DSL modem. Changes mayalso include modifications in the firmware of the CPE DSL modem toaccommodate dynamic data rate changes and implement the associatedsignaling. In some embodiments, the signaling may be accomplished usingthe Embedded Operation Channel (EOC) with a combination of new and/orexisting messages, where some of the new messages may be structured byusing some of the existing undefined Opcodes reserved for future useand/or some of the Opcodes reserved for vendor proprietary use.

In various embodiments, the data rates for the upstream and downstreamdata flows are handed independently. For example, each direction mayhave separately provisioned rates, separate service request changes,separate noise margin measurements, separate threshold adjustmentcriteria, separate achievable rates, and separate assigned rates.Alternatively, data rates for the upstream and downstream data flows maybe handled as a single entity. Various combinations are also possible,in accordance with the invention, where certain aspects, e.g.,adjustment threshold criteria, may be uniform for the downstream andupstream directions, but assigned data rates may be different for eachdirection.

Various embodiments of the invention may distribute the variousfunctions of the invention, differently between the various componentsof the system. For example, in some embodiments, downstream requests fornew data rates are generated in the DSLAM modem, while the CPE DSL modemshall provide SNR and ATN information to the DSLAM modem, whenrequested. In other embodiments, the CPE DSL modem performs SNR/ATNmeasurements, calculates downstream noise margins, and initiates andsends requests for downstream data rate changes to the DSLAM modem.

The methods and apparatus of the present invention may be utilized on avariety of DSL type systems, e.g., Asymmetric Digital Subscriber Line(ADSL), RADSL (Rate-Adaptive DSL), Very High Data Rate Subscriber Line(VDSL), etc.

Numerous additional features and benefits of the methods and apparatusof the present invention are discussed below in the detailed descriptionwhich follows.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates a known initialization sequence used for the ANSIT1.413 standard that takes place between an ATU-C and an ATU-R.

FIG. 2 illustrates an exemplary DSL communications system implemented inaccordance with the present invention.

FIG. 3 illustrates a more detailed representation of the exemplary DSLAMmodem shown in the system of FIG. 2, implemented in accordance with thepresent invention.

FIG. 4 illustrates a more detailed representation of the exemplary CPEDSL modem shown in the system of FIG. 2, implemented in accordance withthe present invention.

FIG. 5 shows a flowchart illustrating a method of dynamic upstream DSLmodem data rate adjustment, in accordance with the present invention.

FIG. 6 shows a flowchart illustrating a method of dynamic downstream DSLmodem data rate adjustment, in accordance with the present invention.

FIG. 7 shows a flowchart illustrating another method of dynamicdownstream DSL modem data rate adjustment, in accordance with thepresent invention.

FIG. 8 illustrates exemplary signaling exchanges between an exemplaryDSLAM modem and an exemplary CPE DSL modem used to explain the presentinvention.

FIG. 9 shows a table identifying some EOC Message Opcodes that maybeused to communicate information in accordance with the present inventionin some implementations of the present invention.

DETAILED DESCRIPTION

The present invention is directed to methods and apparatus which allowfor transitions in DSL line rates in response to changes in lineconditions and/or subscriber request for changes in service withoutinterfering with on-going communications sessions as may occur in thecase where a full re-initialization operation is used to implement arate change.

FIG. 2 illustrates an exemplary DSL communications system 200 usingapparatus implementing the methods of the present invention.Communications system 200 includes a central office 202 and a computer204 located at a customer site. The central office 202 includes a DSLAM206 including a DSLAM modem 208, a provisioning system 210, a billingsystem 212 and a network interface 214. DSLAM 206, provisioning system210, and billing system 212 are coupled together via bus 218 over whichthe various elements 206, 210, and 212 can interchange data andinformation. Provisioning system 210 stores user service level profiles,receives and processes service level request changes, supplies userprovisioned service level information to the DSLAM 206 to the controlmaximum data rate at DSLAM modem 208 for each specific user, andforwards provisioning information tracking user connection times atspecific data rates to the billing system 212. The billing system 212receives information from the provisioning system 210 and/or the DSLAM206 allowing the central office 202 to track and bill each user for theservice level provided. DSLAM 206 is also coupled to network interface214 via link 216 providing the DSLAM 206 and its Modem 208 with aninterface to the Internet 220 and effectively coupling DSLAM modem 208to other modems and other users in addition to the user at computer site204. DSLAM modem 208 provides a DSL interface to customer site computer204, accepts service level provisioning information from provisioningsystem 210, forwards current service level information to billing system212, monitors DSL line 244 for current quality of service and faults,controls the data rates on the DSL line 244, executes initializationsequences, and controls (assigns) data rates on the DSL line 244.

The computer 204, at the customer site includes a CPE DSL modem 222, atelephone modem 224, a CPU 226, input devices 228, output devices 230,and memory 232 coupled together via bus 242, over which the variouselements can interchange data and information. Input devices 228 mayinclude microphones, keyboards, keypads, video recording devices, etc.Output devices 230 may include speakers, video displays, printers, etc.Memory 232 may include applications routines 234 includingvideoconference routines 236, voice (telephone) routines 238, and IP(internet browser) routines 240. Each application software routine 236,238, 240 may be associated with a different desired level of bandwidth,e.g., a different requested data rate for DSL modem 222 corresponding toeach routine 236, 238, 240. CPU 226 executes routines and uses thedata/information in memory 232 to control the functionality of computer204 including the interaction between the modems 222, 224 with the I/Odevices 228, 230, to implement the various application software routines234, and to process service level change requests. Such request may becommunicated to the provisioning system over the Internet or bytelephone. Link 246, e.g., a twisted pair connection, couples thetelephone modem 224 of the customer's computer 204 to the provisioningsystem 210 at central office 202. Telephone modem 224 may convey changein service level requests to provisioning system 210. DSL line 244couples CPE DSL modem 222 to DSLAM modem 208. CPE DSL modem 222 providesthe user of computer 204 with a DSL interface to the central office 202via DSLAM modem 208. DSL modem 222 forwards and receives userinformation, e.g., voice, video, data, to or from a correspondent uservia DSLAM modem 208, forwards service level provisioning requests toprovisioning system 210, monitors the DSL line 244 for current qualityof service and faults, requests data rates on the DSL line 244, providesline quality reports e.g., SNR/ATN info to DSLAM modem 208, executesinitialization sequences and executes data rate change sequences.

A user of computer 204 may generate a service level change requestduring operation of modem 222, and the change request may be processedand implemented without a disruption of service of modem 222 or the needto re-initialize modem 222, in accordance with the invention. Theservice level change request may be a long term change, e.g., userprofile type changes, and/or short term or temporary changes, e.g.,application driven changes, requesting a new service level for a periodof user time while the user is connected. For example, a user may make along term profile change, e.g., subscribe to a plan with a higheravailable DSL data rate, via an input device 228 such as a telephone ora keyboard, while a short term application driven temporary servicelevel request change may be automatically generated by CPU 226 due toexecution of specific application routines 236, 238, 240. For example,if the user of computer 204 is operating on voice application software238, and is communicating over DSL 244 via CPE DSL modem 222 at arelatively low assigned data rate, e.g., bandwidth, and now decides tostart a video conference using video conference software 238, anautomatic request for increased bandwidth may be generated. Similarly,after the videoconference is over and software 236 terminates, a requestfor a decrease in bandwidth may be generated. This short term ortemporary service level change capability, in accordance with theinvention, would allow for additional “bandwidth-on-demand” requestsdynamically providing, “on-the fly” data rate changes without aninterruption in service.

Computer 204 sends the service level change request to the provisioningsystem 210 in the central office 202. The service level change requestsmay be via telephone modem 224 over link 246 to the provisioning system210, or the request may be sent through CPE DSL modem 222, DSL line 244,DSLAM DSL modem 208, and central office bus 218 to provisioning system210 in the normal data flow thru DSL modem 208. Provisioning system 210receives and processes service level request changes from customers,e.g., the user of computer 204. The provisioning system 210 notifies theDSLAM modem 208 and/or the billing system 212 of the service levelchange request. The DSLAM modem 208 in conjunction with the CPE DSLmodem 222, via line measurements, e.g., SNR and ATN, and the interchangeof information with modem 222, determines the maximum achievable DSLline 244 data rate. Then the DSLAM modem 208 determines if the line datarate requested, via the provisioning change request, can be supported,and, if possible, assigns a new line data rate, communicates that newrate to the CPE DSL modem 222, communicates the change in data rate tothe billing system 212, and implements the new data rate dynamically,without the interruption in communications between DSLAM modem 208 andCPE DSL modem 222 or the need to reinitialize and resynchronize, inaccordance with the present invention.

The DSLAM CPU periodically checks the condition of the DSL line 244 fornoise margin based on line condition measurements, e.g., SNR and ATNmeasurements, performed by the DSLAM modem 208 and/or the CPE DSL modem222 during normal communications. If the noise margin is determined tobe low by either the DSLAM modem 208 or the CPE DSL modem 222, the DSLAMmodem 208 can, in accordance with the invention, dynamically change theassigned data rate to a lower value before synchronization is lost,convey the new assigned value to the CPE DSL modem 222 and the billingsystem 212, and implement the new data rate on DSL line 244 dynamicallywithout re-initialization or an interruption in service. If the noisemargin is determined to be high enough to support an increased datarate, and the user is subscribed/provisioned for the higher data rate,the DSLAM modem 208 can, in accordance with the invention dynamicallychange the assigned data rate to a higher value, convey the new assignedvalue to the CPE DSL modem 222 and the billing system 212, and implementthe new data rate on DSL line 244 dynamically without re-initializationor an interruption in service. Therefore, DSLAM modem 208 in conjunctionwith CPE DSL modem 222, via noise margin monitoring and signalingexchanges, is able to identify and dynamically adjust (up or down),without interruption of service, loss of synchronization,re-initialization, or re-power, the DSL data rate to operate at thehighest service level currently provisioned which is currentlyachievable.

FIG. 3 provides a more detailed representation of the DSLAM Modem 208,implemented in accordance with the present invention, of the exemplaryDSL communications system 200 of FIG. 2. DSLAM modem 208 includes a DSLinterface 302, a CPU 304, a network interface 306, a LAN interface 308,and memory 310 coupled together via bus 3.12 over which the variouselements 302, 304, 306, 308, and 3.10 can interchange data andinformation. Memory 310 includes routines 318 and data/information 320.DSL interface 302 provides a port coupled to DSL line 244 providing theDSL connection to a CPE DSL modem 222. The DSL line data rate throughinterface 302 is controlled in accordance with the methods of thepresent invention. In general, the DSL line data rate in terms ofprovisioning, noise margin monitoring, requested rate changes, andassigned rate changes may be handled independently for the upstreamdirection and the downstream direction. The upstream direction isdefined as data/information flow direction from the CPE DSL modem 222 tothe DSLAM modem 208, while the downstream direction is defined as thedata/information flow direction from the DSLAM modem 208 to the CPE DSLmodem 222. Typically, the SNR and ATN for each DSL line directional floware measured by the destination device of the data/information flow,e.g., DSLAM modem 208 monitors upstream signal flow SNR and ATN, whileCPE DSL modem 222 monitors downstream signal flow SNR and ATN. Measuredinformation may be interchanged between the two devices 208 and 222.Requests for changes in data rates may be made by CPE DSL modem 222;however, assignments of upstream and downstream data rates are made byDSLAM modem 208. CPU 304 executes the routines 318 and uses thedata/information 320 included in memory 310, to control the basicfunctionality and implement the new features of the invention in themodem 208. Network interface 306 couples DSLAM modem 208 via link 216 tothe central office network interface 214 and to the INTERNET. LANinterface 308 couples DSLAM modem 208, via central office bus 218, toprovisioning system 210 and billing system 212. DLAM modem 208 canreceive service level change requests and forward assigned data rateinformation through LAN interface 308.

Routines 318 includes communications routines 322, I/O routines 324,initialization routine 326, downstream provisioning adjustment routine328, upstream provisioning adjustment routine 330, downstreamperformance monitoring (noise margin) & rate adjustment routine 332,upstream performance monitoring (noise margin) and rate adjustmentroutine 334, line monitoring fault detection routines 336, downstreamDSLAM assigned data rate change implementation routine 338, and upstreamDSLAM assigned data rate change implementation routine 340.

Data/Information 320 includes data 342, service level request changeinformation 344, downstream subscribed data rate information 346,upstream subscribed data rate information 348, downstream noise margininformation 350 upstream noise margin information 358, downstream rateadjustment criteria 366, upstream rate adjustment criteria 372, maximumpossible downstream data rate 378, maximum possible upstream data rate380, assigned downstream data rate 382, and assigned upstream data rate384.

Data 342 includes user data, e.g., voice, video, and data filestransmitted upstream via DSL line 244 to DSLAM modem 208 from user ofcomputer 204 at a customer site or voice, video, data files intended tobe transmitted by DSLAM modem 208 downstream via DSL line 244 to a userof computer 204. Service level request change information 344 includesinformation received by modem 208 from provisioning system 210 which maytrigger activation of the downstream or upstream provisioning adjustmentroutines 328, 330. Service level change request information 344 may alsoinclude information defining the type of change request, e.g.,upstream/downstream, long term subscriber profile type change/short termapplication driven data rate on demand type change, specific rate changelevel, and specific duration for requested change to be implemented.Downstream subscribed data rate 346 is the current maximum DSLdownstream data rate that DSLAM modem 208 may assign for the user of CPEDSL modem 222 based on provisioning system 210 authorization. Upstreamsubscribed data rate 348 is the current maximum DSL upstream data ratiothat DSLAM modem 208 may assign for the user of CPE DSL modem 222 basedon provisioning system 210 authorization. The provisioning system 210supplies downstream/upstream subscribed data rate information 346, 348to DSLAM modem 208. In accordance with the invention, thedownstream/upstream subscribed data rates 346, 348 may changedynamically, as service level requests are processed, duringcommunication sessions between users without interruptions of service.Downstream noise margin information 350 includes downstream ATN 352,downstream SNR 354, and downstream noise margin 356. Downstream ATN 352is the downstream signal attenuation measured at CPE DSL modem 222,while downstream SNR 354 is the downstream SNR measured at the CPE DSLmodem 222. In some embodiments, downstream noise margin 356 is anensemble of the downstream ATN 352, the downstream SNR 354, and/or otherdownstream line quality information collected where filtering and/orweighting may have been used to determine the downstream noise marginvalue(s) 356. In other embodiments, the SNR 354, by itself, is used asthe downstream noise margin. Upstream noise margin information 358includes upstream ATN 360, upstream SNR 362, and an upstream noisemargin 364. Upstream ATN 360 is the upstream signal attenuation measuredat DSLAM modem 208, while upstream SNR 362 is the upstream SNR measuredat the DSLAM modem 208. In some embodiments, upstream noise margin 364is an ensemble of the upstream ATN 360, the upstream SNR 362, and/orother line quality information collected where filtering and/orweighting may have been used to determine the upstream noise marginvalue(s) 364. In other embodiments the SNR 362, by itself, is used asthe upstream noise margin. Downstream and upstream line rates may becontrolled using separate adjustment thresholds or the same thresholdsdepending on the embodiment.

Downstream rate adjusting criteria 366 includes a downstream increasingadjusting threshold 368 and a downstream decreasing adjustment threshold370. The downstream increasing adjustment threshold 370 is a pre-definedlevel, which when exceeded by the downstream noise margin 356, mayresult in a dynamic downstream data rate increase without interruptionof service. The downstream increasing threshold may be, e.g., an SNR of15 dB in a system where an SNR of 6 dB causes a loss of synchronizationwhile an exemplary downstream decreasing threshold may be, e.g., 9 dB.

The downstream decreasing adjustment threshold 370 is used to trigger adecrease in the downstream line rate when the measured SNR drops belowthe threshold. The downstream decreasing adjustment threshold 370 is apre-defined level. When it is detected that the downstream noise margin356 has dropped below the downstream decreasing adjustment threshold370, the downstream data rate is decreased, without interruption ofservice, e.g., without performing a resynchronization operation.

Upstream rate adjusting criteria 372 includes an upstream increasingadjusting threshold 374 and an upstream decreasing adjustment threshold376. The upstream increasing adjustment threshold 374 is a pre-definedlevel, which when exceeded by the upstream noise margin 364, results ina dynamic upstream data rate increase without interruption of service,e.g., without performing a resynchronization operation. The upstreamdecreasing adjustment threshold 376 is a pre-defined level. When it isdetected that the upstream noise margin 364 has dropped below theupstream decreasing adjustment threshold 376, the upstream data rate maydecreased, without interruption of service. In some embodiments,downstream noise margin information 350 and/or the downstream rateadjustment criteria 366 may not be included in the DSLAM modem 208, asin such cases the CPE DSL modem 222 performs the downstream performancemonitoring and evaluation, subsequently forwarding data rate downstreamchange requests to DSLAM modem 208. Maximum possible downstream datarate 378 is the determined maximum achievable downstream data rate thatcould be assigned while still maintaining synchronization andmaintaining a specified Bit Error Rate (BER), based upon the downstreamnoise margin measurements 356. Maximum possible upstream data rate 380is the determined maximum achievable upstream data rate that could beassigned while still maintaining synchronization and maintaining aspecified Bit Error Rate (BER), based upon the upstream noise marginmeasurements 364. Assigned downstream data rate 382 is the operationaldownstream data rate which is controlled and set by the DSLAM modem 208and conveyed to the CPE DSL modem 222. Assigned downstream data rate 382is limited by both the downstream subscribed data rate 346 and themaximum possible downstream data rate 378. Assigned upstream date rate384 is the operational upstream data rate which is controlled and set bythe DSLAM modem 208 and conveyed to the CPE DSL modem 222. Assignedupstream data rate 384 is limited by both the upstream subscribed daterate 348 and the max possible upstream date rate 380.

Communications routines 322 include the protocols, e.g., T1.413 and ITUG.dmt (G.hs) used by the DSLAM modem 208 in communications with CPE DSLmodems 222. I/O routines 324 may control operation of the variousinterfaces: DSL interface 302, network interface 306, and LAN interface308. I/O routines 324 may be invoked by other routines to control thetransfer of information, e.g., downstream noise margin information 350and service level request change information 344, the dynamic resettingof port configurations, e.g., when directed to use a new assigneddownstream/upstream data rate 382, 384.

Initialization routine 326 controls the initialization sequence or modemtraining, communication and negotiation of capabilities, and thetraining of the transceivers, e.g., in DSL interface 302 using thenegotiated parameters. The negotiation of capabilities may involve:sending test signals on the DSL line, measuring SNR and ATN at thereceiving end of the DSL, obtaining initial values for maximum possibledownstream/upstream rates 378, 380, transferring initialdownstream/upstream subscribed data rate information 346, 348 from theprovisioning system 210, and calculating and assigning initial maximumpossible downstream/upstream rate values 378, 380.

Downstream provisioning adjustment routine 328 in DSLAM modem 208 worksin coordination with a downstream provisioning adjustment routine 422(FIG. 4) in CPE DSL modem 222 to respond to a service level requestchange 344, and using downstream noise margin info 350 determines amaximum possible downstream rate 378 for the given line conditions. Thenroutine 328 determines, using the current downstream subscribed datarate 346, whether a new downstream data rate should be set by the DSLAMmodem 208. Upstream provisioning adjustment routine 330 in DSLAM modem208 responds to a service level request change 344, and using upstreamnoise margin 364, determines a maximum possible upstream rate 380 forthe given line conditions, and then determines, using the currentupstream subscribed data rate 348, whether a new upstream data rateshould be set by the DSLAM modem 208. In accordance with the invention,downstream/upstream provisioning adjustment routines 328, 330 maycontrol dynamic service level (data rate) changes in either direction(up/down), during a communication session, without a disruption inservice.

Downstream performance monitoring (noise margin)& rate adjustmentroutine 332 in DSLAM modem 308 operates in conjunction with downstreamperformance monitoring (noise margin) & rate adjustment routine 424 inCPE DSL modem 222 to monitor downstream ATN 352 and downstream SNR 354obtaining downstream noise margin 356, evaluating whether the downstreamnoise margin 356 has exceeded boundaries defined by the downstream rateincreasing adjustment threshold 368 and the downstream rate decreasingadjustment threshold 370, and generating a request for a new downstreamdata rate, if so directed. Downstream performance monitoring (noisemargin) & rate adjustment routine 332 repeats on an ongoing basis, e.g.,periodically, during normal operation, providing for the periodicchecking of the DSL downstream line quality to identify whether a higherdownstream rate, prescribed per the downstream subscribed data rate 346is achievable or whether the current assigned downstream data rate 382is not sustainable. Routine 332 thus identifies downstream data rateadjustments that may be made so that the customer may achieve thehighest possible throughput on their DSL line 244 consistent with theirprescribed service rate 346. In accordance with the invention, thedownstream performance monitoring (noise margin) & rate adjustmentroutine 322 regulates the assigned downstream data rate 382 in bothdirections (up/down) as line conditions change without disrupting normaloperations or service.

Upstream performance monitoring (noise margin) & rate adjustment routine334 monitors upstream ATN 360 and upstream SNR 362, obtains an upstreamnoise margin 364, evaluates whether the upstream noise margin 364 hasexceeded boundaries defined by the upstream rate increasing adjustmentthreshold 374 and the upstream rate decreasing adjustment threshold 376,and generates a request for a new upstream data rate, if so directed.Upstream performance monitoring (noise margin) & rate adjustment routine334 repeats on an ongoing basis, e.g., periodically, during normaloperation, providing for the periodic checking of the DSL upstream linequality to identify whether a higher upstream rate, prescribed per theupstream subscribed data rate 348 is achievable, or whether the currentassigned upstream data rate 384 is not sustainable. Routine 334 thusidentifies upstream data rate adjustments that may be made so that thecustomer may achieve the highest possible throughput on their DSL line244 consistent with their prescribed service rate 348. In accordancewith the invention, the upstream performance monitoring (noise margin) &rate adjustment routine 334 regulates the assigned upstream data rate384 in both directions (up/down) as line conditions change withoutdisrupting normal operations or service.

Line monitoring fault detection routines 336 monitors the DSL line forloss of signal, loss of frame, loss of power, and processes informationfrom CPE DSL 222 indicating far-end loss-of signal, far-end remotefailure indication, and far-end loss-of power. Due to fault indications,routine 336 may evoke the initialization routine 326 to attempt toreestablish valid communications with CPE DLS modem 222.

Downstream DSLAM assigned data rate change implementation routine 338 inDSLAM modem 208 in conjunction with downstream DSLAM assigned data ratechange implementation routine 428 in CPE DSL modem 222 controls theimplementation of rate changes called for as output from the downstreamprovisioning adjustment routine 328 and/or the downstream performancemonitoring (noise margin) & rate adjustment routines 332, 424. Theimplementation of the rate change is performed via a signaling exchangebetween DSLAM modem 208 and CPE DSL modem 222. Assignment routine 338directs DSLAM modem 208 to set the new assigned downstream data rate382, signals the new rate to the CPE DSL modem 222, and activates thenew data transfer rate. The transition to the new assigned downstreamdata rate 382 shall be performed dynamically without disrupting normaloperations or service, in accordance with the invention.

Upstream DSLAM assigned data rate change implementation routine 340 inDSLAM modem 208 in conjunction with upstream DSLAM assigned data ratechange implementation routine 430 in CPE DSL modem 222 controls theimplementation of rate changes called for as output from the upstreamprovisioning adjustment routine 330 and/or the upstream performancemonitoring (noise margin) & rate adjustment routine 334. Theimplementation of the rate change shall be performed via a signalingexchange between DSLAM modem 208 and CPE DSL modem 222. Assignmentroutine 340 directs DSLAM modem 208 to set the new assigned upstreamdata rate 384, signals the new rate to the CPE DSL modem 222, andactivates the new data transfer rate. The transition to the new assigneddownstream data rate 384 shall be performed dynamically withoutdisrupting normal operations or service, in accordance with theinvention.

FIG. 4 provides a more detailed representation of the CPE DSL Modem 222,implemented in accordance with the present invention, of the exemplaryDSL communications system 200 of FIG. 2. CPE DSL modem 222 includes aDSL interface 402, a CPU 404, a network interface 406, and memory 408coupled together via bus 410 over which the various elements 402, 404,406, 408, and 410 can interchange data and information. Memory 410includes routines 412 and data/information 414. DSL interface 402provides a port coupled to DSL line 244 providing the DSL connection toDSLAM DSL modem 208. The DSL line data rate through interface 402 iscontrolled in accordance with the methods of the present invention. CPU404 executes the routines 412 and uses the data/information 414 includedin memory 408, to control the basic functionality and implement the newfeatures of the invention in the modem 222. Network interface 406couples CPE DSL modem 222 via bus 242 (note: in the figure, bus 242needs to extend outside the 222 box) to the other elements 226, 228,230, 224, and 232 of computer 204.

Routines 412 includes communications routines 416, I/O routines 418,initialization routine 420, downstream provisioning adjustment routine422, downstream performance monitoring (noise margin) & rate adjustmentroutine 424, line monitoring fault detection routines 426, downstreamDSLAM assigned data rate change implementation routine 428, and upstreamDSLAM assigned data rate change implementation routine 430.

Data/Information 414 includes data 432, service level request changeinformation 434, downstream subscribed data rate 436, downstream noisemargin information 438, downstream rate adjustment criteria 446, maximumpossible downstream data rate 452, assigned downstream data rate 454,and assigned upstream data rate 456.

Data 432 includes user data, e.g., voice, video, data files to betransmitted upstream via DSL line 244 to DSLAM modem 208 intended for apeer user at a different site, and received user data, e.g., voice,video, data files originally sourced from a peer user and transmitted byDSLAM modem 208 downstream via DSL line 244 to CPE DSL modem 222.Service level request change information 434 includes informationreceived by modem 222 originally from provisioning system 210 which maytrigger activation of the downstream provisioning adjustment routine422. Service level change request information 434 may also includeinformation defining the type of change request, e.g., long termsubscriber profile type change/short term application driven data rateon demand type change, specific rate change level, and specific durationfor the requested change to be implemented. Downstream subscribed datarate 436 is the current maximum DSL downstream data that DSLAM modem 208may assign. The provisioning system 210 is the original source of thedownstream subscribed data rate information 436 which has been forwardedto modem 222. In accordance with the invention, the downstreamsubscribed data rate 436 may change dynamically, as service levelrequests are processed, during communication sessions between userswithout interruptions of service. Downstream noise margin information438 includes downstream ATN 440, downstream SNR 442, and downstreamnoise margin 444. Downstream ATN 440 is the downstream signalattenuation measured at CPE DSL modem 222, while downstream SNR 442 isthe downstream SNR measured at CPE DSL modem 222. Downstream noisemargin 444 represents an ensemble of the downstream ATN 440, thedownstream SNR 442 and/or other line measurements, where filteringand/or weighting may have been used to determine the downstream noisemargin value 444. Downstream rate adjusting criteria 446 includes adownstream increasing adjusting threshold 448 and a downstreamdecreasing adjustment threshold 450. The downstream increasingadjustment threshold 448 is a pre-defined level, which when exceeded bythe downstream noise margin 444, may result in a dynamic downstream datarate increase without interruption of service. The downstream decreasingadjustment threshold 450 is a pre-defined level. If it is detected thatthe downstream noise margin 444 has dropped below the downstreamdecreasing adjustment threshold 450, then a dynamic downstream data ratedecrease may occur without an interruption in service. Maximum possibledownstream data rate 452 is the determined maximum achievable downstreamdata rate that could be assigned while still maintaining synchronizationand maintaining a specified Bit Error Rate (BER), based upon thedownstream noise margin information 438. Assigned downstream data rate454 is the operational downstream data rate which is controlled and setby the DSLAM modem 208 and has been conveyed to the CPE DSL modem 222.Assigned downstream data rate 454 is limited by both the downstreamsubscribed rate 436 and the maximum possible downstream data rate 452.Assigned upstream data rate 456 is the operational upstream data ratewhich is controlled and set by the DSLAM modem 208 and has been conveyedto the CPE DSL modem 222.

Communications routines 416 include the protocols, e.g., T1.413 and ITUG.dmt (G.hs) used by the CPE DSL modem 222 in communications with DSLAMmodem 208. I/O routines 418 may control operation of the variousinterfaces: DSL interface 402 and network interface 406. I/O routines418 may be invoked by other routines to control the transfer ofinformation, e.g., downstream noise margin information 438 and servicelevel request change 434, and the dynamic resetting of portconfigurations, e.g., when directed to use a new assigneddownstream/upstream data rate 454, 456. Initialization routine 420controls the initialization sequence or modem training, communicationand negotiation of capabilities, and the training of the transceivers,e.g., in DSL interface 402 using the negotiated parameters. Thenegotiation of capabilities may involve: the sending of test signals onthe DSL line, the measurement of SNR and ATN at the receiving end of theDSL line, obtaining initial values for maximum possible downstream datarates 452, the transfer of initial downstream subscribed data rate 436originating from the provisioning system 210, and the reception ofinitial assigned downstream/upstream rate values 454, 456.

Downstream provisioning adjustment routine 422 in CPE DSL modem 222works in coordination with a downstream provisioning adjustment routine328 in DSLAM modem 208 to respond to a service level request change 434,and using downstream noise margin information 438, determines a maximumpossible downstream data rate 452 for the given line conditions, andthen determines, using the current downstream subscribed data rate 436,whether a new downstream data rate should be set by the DSLAM modem 208.In accordance with the invention, downstream provisioning adjustmentroutine 422 may forward downstream data rate change requests to DSLAMmodem 208 for dynamic service level (data rate) changes in eitherdirection (up/down), during a communication session, without adisruption in service.

Downstream performance monitoring (noise margin) & rate adjustmentroutine 424 in CPE DSL modem 222 operates in conjunction with downstreamperformance monitoring (noise margin) & rate adjustment routine 332 inDSLAM modem 208 to monitor downstream ATN 440 and downstream SNR 442obtaining a downstream noise margin 444, evaluating whether thedownstream noise margin 444 has exceeded boundaries defined by thedownstream increasing adjustment threshold 448 and the downstreamdecreasing adjustment threshold 450, and generating a request for a newdownstream data rate, if so directed. Downstream performance monitoring(noise margin) & rate adjustment routine 424 repeats on an ongoingbasis, e.g. periodically, during normal operation, providing for theperiodic checking of the DSL downstream line quality to identify whethera higher downstream rate, prescribed per the downstream subscribed datarate 436 is achievable or whether the current assigned downstream datarate 454 is not sustainable. Routine 424 thus identifies downstream datarate adjustments that may be made so that the customer may achieve thehighest possible throughput on their DSL line 244 consistent with theirdownstream subscribed service rate 436, and forwards those requests toDSLAM DSL modem 208. In accordance with the invention, the downstreamperformance monitoring (noise margin) & rate adjustment routine 424regulates the assigned downstream data rate 454 in both directions(up/down) as line conditions change without disrupting normal operationsor service.

Line monitoring fault detection routines 426 monitors the DSL line 244for loss of signal, loss of frame, loss of power, and far-end loss ofsignal. Due to fault indications, routine 426 may evoke theinitialization routine 420 to attempt to reestablish validcommunications with DSLAM modem 208.

Downstream DSLAM assigned data rate change implementation routine 428 inCPE DSL modem 222 receives new assigned downstream data rates 454 fromthe downstream DSLAM assigned data rate change implementation routine338 in DSLAM 208, acknowledges reception, and transitions to the newdata rate. The transition to the new assigned downstream data rate 454shall be performed dynamically without disrupting normal operations orservice, in accordance with the invention.

Upstream DSLAM assigned data rate change implementation routine 430 inCPE DSL modem 222 receives new assigned upstream data rates 456 from theupstream DSLAM assigned data rate change implementation routine 340 inDSLAM modem 208, acknowledges reception, and transitions to the new datarate. The transition to the new assigned upstream data rate 456 shall beperformed dynamically without disrupting normal operations or service,in accordance with the invention

FIGS. 5-7 illustrate flow charts implementing the methods of the presentinvention. With respect to the flow charts of FIGS. 5-7, the followingshorthand notation is used for convenience, DSLAM=DSLAM modem, andMODEM=CPE DSL modem.

FIG. 5 shows a flowchart 500 illustrating a method of dynamic upstreamDSL modem data rate adjustment, in accordance with the presentinvention. Flow chart 500 is subdivided into 3 major subsections: theupstream provisioning rate adjustment section 502, the upstreamperformance monitoring/rate adjustment section 504, and the upstreamdata rate change section 506. Upstream provisioning rate adjustmentsection 502 is performed under the control of the upstream provisioningadjustment routine 330 in DSLAM modem 208. Upstream performancemonitoring/rate adjustment section is performed under the direction ofthe upstream performance monitoring (noise margin) & rate adjustmentroutine 334 in DSLAM modem 208. The upstream data rate changeimplementation section is controlled by the upstream DSLAM assigned datarate change implantation routines 340, 430 in modems 208, 222.

Following completion of modem initialization and selection of anassigned upstream date rate 384, subsection 504 is activated, and theupstream performance monitoring starts in step 508. Operation proceedsto step 510, where DSLAM modem 208 monitors the current upstreamsignaling and determines an upstream noise margin 364 based uponmeasured upstream ATN 360 and upstream SNR 362. The upstream noisemargin 364 is determined on an ongoing basis, e.g., periodically. Thetime intervals between new determinations of the upstream noise margin364, e.g., 1 ms to 1 hr, may be determined by a number of settings inthe configuration parameters stored in the DSLAM modem 208 and/or theCPE DSL modem 202. Proceeding to step 512, for each determined upstreamnoise margin 364, a test is made as to whether the upstream signal datarate, e.g., the assigned upstream data rate 384, should be lowered dueto a low noise margin. The test involves comparing the upstream noisemargin 364 to the upstream decreasing adjustment threshold 376. Theupstream decreasing adjustment threshold 376 has been pre-selected at alevel which will result in a transition to a lower upstream assigneddata rate 384, before synchronization is lost, resulting in smoothdynamic transitions to the lower rate. If the upstream noise margin 364is lower than the upstream decreasing adjustment criteria 376, then flowproceeds to step 514, where a new upstream rate is calculated bydecrementing the current assigned upstream rate 384 by one step size.The new upstream data rate will be forwarded to step 534 of the upstreamdata rate change implementation section 506. However, in step 512, ifthe upstream noise margin 364, exceeds the upstream decreasingadjustment threshold 376, it has been determined that the upstream noisemargin 364 is at least high enough to support the current upstreamassigned rate 384, and so operation proceeds to step 516. In step 516,the upstream noise margin 364 is tested against the upstream increasingadjustment threshold 374 to determine if there is sufficient margin toratchet up the assigned upstream data rate 384. If the upstream noisemargin 364 exceeds the upstream increasing adjustment threshold 374, theline conditions can support a higher data rate, and therefore flowproceeds to step 518. In step 518, a new upstream data rate iscalculated by increasing the current assigned upstream data rate 384 byone step size. Next, in step 520, the new upstream data rate is comparedto the upstream subscribed data rate 348. If the new upstream data rateis <the upstream subscriber rate 348, then the new upstream data rate isforwarded to step 534 of the upstream data rate change implantationsection 506; otherwise flow returns to via connection node A 522 to step510. Returning to step 516, if it was determined that the upstream noisemargin 364 did not exceed the upstream increasing adjustment threshold374, then the DSL is currently operating at the present maximum capacityand no action should be taken, so flow proceeds via connection node 522back to step 510.

In parallel to the noise monitoring of section 504, the upstreamprovisioning rate adjustment section 502 may be executed. Operationstarts in step 524 where the provisioning system 210, processes aservice level request change from a user. The service level requestchange may be either a provisioning request, e.g., a subscriber profilechange, or an application driven temporary service level request for achange in change in bandwidth, e.g., on-demand high bit rate services.The request may have been routed to the provisioning system viacommunications through telephone modem 224 or through MODEM 222;however, in either case, services are not interrupted by the request. Asa result of step 524, the provisioning system 210, signals the billingsystem 212 providing notification of the change in user service level,and the provisioning system 210 also signals the DSLAM 208 by sendingthe service level request change 344 and the new upstream subscribeddata rate 348. Next in step 530, the DSLAM 208, determines the maximumpossible upstream data rate 380 using the current upstream noise margininformation 358, e.g., upstream ATN 360 and upstream SNR 362. In step532, the DSLAM 208 determines if the upstream assigned data rate 384should be increased by evaluating if maximum possible upstream data rate380 exceeds the current assigned upstream data rate 384 and does notexceed the upstream subscribed data rate 348. In step 532, the DSLAMmodem determines if the assigned upstream data should be decreased ifthe new upstream subscribed data rate is below the current assignedupstream data rate 384. If dictated, a new upstream data rate iscalculated in step 532 and forwarded to step 534 of the upstream datarate change implementation section 506. In some embodiments, the datarate—when increased—is increased in single step sizes. If it isdetermined in step 532, that the assigned upstream data rate cannot bechanged at the present time, due to line conditions, no action is taken;however, the new upstream subscribed data rate 348 has been loaded intothe DSLAM 208, allowing the upstream performance monitoring section 504to make the adjustment to a new assigned upstream data rate 384, at alater time, whenever line conditions dictate that it is supportable.

The upstream data rate change implementation section 506 of flowchart500 will now be described. In step 534, the DSLAM 208, receives a newrequested upstream data rate, either from an output of the noisemonitoring section 504 in steps 514 or 520 or from the provisioningsection 502 in step 532, and sets the DSLAM assigned upstream data rate384 to the new requested value. Proceeding to step 536, the DSLAM 208conveys the new assigned upstream data rate 384 to the MODEM 222 via,e.g., a write new data rate message. MODEM 222 stores the new data rateas assigned upstream data rate 456 and sends an acknowledgement signalback to DSLAM 208. The MODEM 222 changes to operate at the new upstreamassigned data rate 456 in step 540. In step 542, the MODEM 222 and theDSLAM 208 operate at the new data rate, the transition having beenwithout interruption of service, in accordance with the invention. Nextflow proceeds via connection node A 522 back to performance monitoringof step 510, where new noise margin are determined.

FIG. 6 shows a flowchart 600 illustrating a method of dynamic downstreamMODEM data rate adjustment, in accordance with the present invention.Flow chart 600 is subdivided into 3 major subjections: the downstreamprovisioning rate adjustment section 602, the downstream performancemonitoring/rate adjustment section 604, and the downstream data ratechange implementation section 606. The downstream provisioning rateadjustment section 602 is performed under the control of the downstreamprovisioning adjustment routines 328, 422 in DSLAM 208 and in MODEM 222.The downstream performance monitoring/rate adjustment section 604 isperformed under the direction of the downstream performance monitoring(noise margin) & rate adjustment routines 332, 424 in modems 208, 222.The downstream data rate change implementation section 606 is controlledby the downstream DSLAM assigned data rate change implementationroutines 338, 428 in modems 208, 222.

Following completion of modem initialization and selection of adownstream assigned date rate 382, subsection 604 is activated, and thedownstream performance monitoring starts in step 608. Operation proceedsto step 610, where MODEM 222 monitors the current downstream signaling,measures a downstream ATN 440 and a downstream SNR 442, and stores theinformation in its registers. The process of step 610 is repeated on anongoing basis, e.g., periodically. In step 612, DSLAM 208, sends readdata register messages to the MODEM 222, to request downstream ATN 440and downstream SNR 442. The request of step 612 is performed on anongoing basis, e.g., periodically. The rate chosen for measuring the ATN440 and the SNR 442 in step 610 may be different than the rate chosenfor accessing the information in step 612. In some embodiments, the rateof step 610 is at least twice the rate of step 612. The time intervalsbetween successive measurements in step 610 and the time intervalsbetween successive access requests of step 612 may be determined by anumber of settings in the configuration parameters stored in the DSLAM208 and/or the MODEM 202. In step 614, MODEM 222 responds and sends therequested information to the DSLAM 208, where the information is storedas downstream ATN 352 and downstream SNR 354. Next, in step 616, theDSLAM determines a downstream noise margin 356, based upon the ATN 352and SNR 354. Proceeding to step 618, for each determined downstreamnoise margin 356, a test is made as to whether the downstream signaldata rate, e.g., the assigned downstream data rate 382, should belowered due to a low noise margin. The test involves comparing thedownstream noise margin 356 to the downstream decreasing adjustmentthreshold 370. The downstream decreasing adjustment threshold 370 hasbeen pre-selected at a level which will result in a transition to alower downstream assigned data rate 382, before synchronization is lost,resulting in smooth dynamic transitions to the lower rate. If thedownstream noise margin 356 is lower than the downstream decreasingadjustment criteria 370, then flow proceeds to step 620, where a newdownstream rate is calculated by decrementing the current assigneddownstream data rate 382 by one step size. In some embodiments, eachstep size may a uniform increment, e.g., 32 Kbps based upon the bin sizespecified by the standard, e.g., ITU G.992.1 G. DMT. The new downstreamdata rate will be forwarded to step 644 of the downstream data ratechange implementation section 606. However, in step 618, if thedownstream noise margin 356, exceeds the downstream decreasingadjustment threshold 370, it has been determined that the downstreamnoise margin 356 is at least high enough to support the currentdownstream assigned data rate 382, and so operation proceeds to step622. In step 622, the downstream noise margin is tested against thedownstream increasing adjustment threshold 368 to determine if there issufficient margin to ratchet up the assigned downstream data rate 382.If the downstream noise margin 356 exceeds the downstream increasingadjustment threshold 368, the line condition can support a higher datarate, and therefore flow proceeds to step 624. In step 624, a newdownstream data rate is calculated by increasing the current assigneddownstream data rate 382 by one step size. Next, in step 626, the newdownstream data rate is compared to the downstream subscribed data rate346. If the new downstream data rate is <the downstream subscribed datarate 346, then the new downstream data rate is forwarded to step 644 ofthe downstream data rate change implementation section 606; otherwiseflow returns to via connection node B 628 to step 610. Returning to step622, if it was determined that the downstream noise margin 356 did notexceed the downstream increasing adjustment threshold 368, then the DSLis currently operating at the maximum capacity and no action should betaken, so flow proceeds via connection node B 628 back to step 610.

In parallel to the noise monitoring of section 604, the downstreamprovisioning rate adjustment section 602 may be executed. Operationstarts in step 630 where the provisioning system 210, processes aservice level request change from a user. The service level requestchange may be either a provisioning request, e.g., a subscriber profilechange, or an application driven temporary service level request for achange in change in bandwidth, e.g., on-demand high bit rate services.The request may have been routed to the provisioning system 210 viacommunications through telephone modem 224 or through MODEM 222;however, in either case, services are not interrupted by the request. Asa result of step 630, the provisioning system 210 signals the billingsystem 212 providing notification of the change in user service level instep 632, and the provisioning system 210 also signals the DSLAM 208 bysending the service level request change 344 and the new downstreamsubscribed data rate 346 in step 634. Next, in step 636, DSLAM 208 sendsread data register request messages to MODEM 222 to request downstreamATN 440 and downstream SNR 442. In step 638, MODEM 222 responds andsends the information to the DSLAM 208 where it is stored as downstreamATN 352 and downstream SNR 354. In step 640, DSLAM 208 determines themaximum possible downstream data rate 378 based on the given lineconditions obtained in step 638. In step 642, the DSLAM 208 determinesif the downstream assigned data rate 382 should be increased byevaluating if maximum possible downstream data rate 378 exceeds thecurrent assigned downstream data rate 382 and does not exceed thedownstream subscribed data rate 346. In step 642, the DSLAM modem 208determines the assigned downstream data should be decreased if the newdownstream subscribed data rate 346 is below the current assigneddownstream data rate 382. If dictated, a new downstream data rate iscalculated in step 642 and forwarded to step 644 of the downstream datarate change implementation section 606. In some embodiments, where anincrease is called for, the data rate is increased in a single stepsize. If it is determined in step 642, that the assigned downstream datarate 382 cannot be changed at the present time, due to line conditions,no action is taken; however, the new downstream subscribed data rate 346has been loaded into the DSLAM 208, allowing the downstream performancemonitoring section 604 to make the adjustment to a new assigneddownstream data rate 382, at a later time, whenever line conditionsindicate that it is supportable.

The downstream data rate change implementation section 606 of flowchart600 will now be described. In step 644, the DSLAM 208, receives a newrequested downstream data rate, either as output from the downstreamperformance monitoring/rate adjustment section 604 in steps 620 or 626or as output from the downstream provisioning rate adjustment section602 in step 642, and sets the DSLAM assigned downstream data rate 382 tothe new requested value. Proceeding to step 646, the DSLAM 208 conveysthe new assigned downstream data rate 382 to the MODEM 222 via, e.g., awrite new data rate message. MODEM 222 stores the new data rate asassigned downstream data rate 454 and sends an acknowledgement signalback to DSLAM 208. The DSLAM 208 changes to operate at the new assigneddownstream data rate 382 in step 650. In step 652, the MODEM 222 and theDSLAM 208 operate at the new data rate, the transition having beenwithout interruption of service, in accordance with the invention. Nextflow proceeds via connection node B 628 back to performance monitoringstep 610, where new downstream ATN 440 and SNR 442 measurements aremade.

FIG. 7 shows a flowchart 700 illustrating another method of dynamicdownstream DSL modem data rate adjustment, in accordance with thepresent invention. In the implementation of FIG. 7, the MODEM 222determines any new downstream rates and sends a request, when a changein rate is called for, to the DSLAM 208. In the implementation of FIG.6, the MODEM 222 measures downstream signal line characteristics, whichMODEM 222 sends on an ongoing basis to DSLAM 208; the DSLAM 208 uses thetransferred line quality information to decide when a downstream datarate change should be requested. The approach of FIG. 7 has theadvantage of potentially less signaling between modems 208 and 222,while the approach of FIG. 6 has less complexity in the MODEM 222. Flowchart 700 is subdivided into 3 major subjections: the downstreamprovisioning rate adjustment section 702, the downstream performancemonitoring/rate adjustment section 704, and the downstream data ratechange implementation section 706. The downstream provisioning rateadjustment section 702 is performed under the control of the downstreamprovisioning adjustment routines 328, 422 in modems 208, 222. Thedownstream performance monitoring/rate adjustment section 704 isperformed under the direction of the downstream performance monitoring(noise margin) & rate adjustment routines 332, 424 in modems 208, 222.The downstream data rate change implementation section 706 is controlledby the downstream DSLAM assigned data rate change implementationroutines 338, 428 in modems 208, 222.

Following completion of modem initialization and selection of adownstream assigned date rate 382, subsection 704 is activated, and thedownstream performance monitoring starts in step 708. Operation proceedsto step 710, where MODEM 222 monitors the current downstream signaling,measures a downstream ATN 440 and a downstream SNR 442, an determines adownstream noise margin 444. The process of step 710 is repeated on anongoing basis, e.g., periodically. The time intervals between newdeterminations of the downstream noise margin 444, e.g., 1 ms to 1 hr,may be determined by a number of settings in the configurationparameters stored in the DSLAM 208 and/or the MODEM 222. Proceeding tostep 712, for each determined downstream noise margin 444, a test ismade as to whether the downstream signal data rate, e.g., the assigneddownstream data rate 454, should be lowered due to a low noise margin.The test involves comparing the downstream noise margin 444 to thedownstream decreasing adjustment threshold 450. The downstreamdecreasing adjustment threshold 450 has been pre-selected at a levelwhich will result in a transition to a lower downstream assigned datarate 454, before synchronization is lost, resulting in smooth dynamictransitions to the lower rate. If the downstream noise margin 444 islower than the downstream decreasing adjustment threshold 450, then flowproceeds to step 714, where a new downstream rate is calculated bydecrementing the current assigned downstream rate 454 by one step size.The new downstream data rate will be forwarded to step 738 of thedownstream data rate change implementation section 706. However, in step712, if the downstream noise margin 444, exceeds the downstreamdecreasing adjustment threshold 450, it has been determined that thedownstream noise margin 444 is at least high enough to support thecurrent downstream assigned data rate 454, and so operation proceeds tostep 716. In step 716, the downstream noise margin 444 is tested againstthe downstream increasing adjustment threshold 448 to determine if thereis sufficient margin to ratchet up the assigned downstream data rate454. If the downstream noise margin 444 exceeds the downstreamincreasing adjustment threshold 448, the line conditions can support ahigher data rate, and therefore flow proceeds to step 718. In step 718,a new downstream data rate is calculated by increasing the currentassigned downstream data rate 454 by one step size. Next, in step 720,the new downstream data rate is compared to the downstream subscribeddata rate 436. If the new downstream data rate is <the downstreamsubscribed data rate 436, then the new downstream data rate is forwardedto step 738 of the downstream data rate change implementation section706; otherwise, flow returns to via connection node C 722 to step 710.Returning to step 716, if it was determined that the downstream noisemargin 444 did not exceed the downstream increasing adjustment threshold448, then the DSL is currently operating at the maximum capacity and noaction should be taken, so flow proceeds via connection node C 722 backto step 710.

In parallel to the noise monitoring of section 704, the downstreamprovisioning rate adjustment section 702 may be executed. Operationstarts in step 724 where the provisioning system 210, processes aservice level request change from a user. The service level requestchange may be either a provisioning request, e.g., a subscriber profilechange, or an application driven temporary service level request for achange in change in bandwidth, e.g., on-demand high bit services. Therequest may have been routed to the provisioning system 210 viacommunications through telephone modem 224 or through MODEM 222;however, in either case, services are not interrupted by the request. Asa result of step 724, the provisioning system 210 signals the billingsystem 212 providing notification of the change in user service level instep 726, and the provisioning system 210 also signals the DSLAM 208 bysending the service level request change information 344 and the newdownstream subscribed data rate 346 in step 728. Next, in step 730,DSLAM 208 forwards the new downstream subscribed data rate 346 in awrite message to MODEM 222. In step 732, MODEM 222 responds and sends anacknowledgement signal to the DSLAM modem 208. In step 734, MODEM 222determines the maximum possible downstream data rate 452 based on thecurrent line conditions, e.g., downstream ATN 440 and the downstream SNR442. In step 736, MODEM 222 determines if the downstream assigned datarate 454 should be increased by evaluating if maximum possibledownstream data rate 452 exceeds the current assigned downstream datarate 454 and does not exceed the downstream subscribed data rate 436. Instep 736, MODEM 222 determines that the assigned downstream data shouldbe decreased if the new downstream subscribed data rate 436 is below thecurrent assigned downstream data rate 454. If dictated, a new downstreamdata rate is calculated in step 736 and forwarded to step 738 of thedownstream data rate change implementation section 706. In someembodiments, where an increase is called for, the data rate is increasedin a single step size. If it is determined in step 736, that theassigned downstream data rate 454 cannot be changed at the present time,due to line conditions, no action is taken; however, the new downstreamsubscribed data rate 436 has been loaded into the MODEM 222, allowingthe downstream performance monitoring section 704 to make the adjustmentto a new assigned downstream data rate 454, at a later time, wheneverline conditions indicate that it is supportable.

The downstream data rate change implementation section 706 of flowchart700 will now be described. In step 738, the MODEM 222 sends a requestnew data rate message to the DSLAM 208 with the new downstream data ratevalue. The new downstream requested data rate value may have beengenerated as output from the noise monitoring section 704 in steps 714or 720 or as output from the provisioning section 702 in step 736.Proceeding to step 740, the DSLAM 208 receives the new requesteddownstream rate value. In step 742, the DSLAM 208 verifies that the newdownstream requested rate value does not exceed the downstreamsubscribed date rate 346. If the verification check passes in step 742,step 744 is performed where DSLAM 208 sets the assigned downstream datarate 382 equal to the new requested downstream data rate. Next, in step746, the DSLAM 208 sends a write data rate message to MODEM 222,conveying the new assigned downstream data rate 382. In step 748, theMODEM 222 receives the new data rate, updates the assigned downstreamdata rate 454 in its memory 408, and sends back an acknowledgement tothe DSLAM 208. Next in step 750, the DSLAM 208 changes the downstreamdata rate to the new assigned downstream data rate 382. The DSLAMchanges the rates after the modem sends the acknowledgement of therequest In step 752, MODEM 222 and DSLAM 208 operate at the new datarate, the transition having been without interruption of service, inaccordance with the invention. Next flow proceeds via connection node C722 back to performance monitoring step 710, where new downstream ATN440 and SNR 442 measurements are made. Referring back to step 722, if itwas determined that the new requested downstream data rate exceeded thedownstream subscribed data rate 346, the request is denied, a warningmessage may be sent to the MODEM 222 and/or to the provisioning system210, and flow is directed via connection node C 722 back to theperformance monitoring of step 710.

FIG. 8 illustrates exemplary signaling that may be used between DSLAM208 and MODEM 222 during implementation of the methods of the presentinvention in some embodiments. The DSLAM 208, in some embodiments, isresponsible for assigning both the downstream and upstream data rates.The line condition measurements, e.g., SNR and ATN are typicallyperformed at the receiving end.

In some embodiments, the MODEM 222 makes downstream rate adjustmentsrequests to the DSLAM 208. Under such scenarios, a write downstreamprovisional rate message 802 may be sent to the MODEM 222, and MODEM 222will respond by sending an acknowledgement message 804 to the DSLAM 208.If MODEM 222 has knowledge of the downstream provisioned rate, MODEM 222should not generate and transmit extraneous requests for higher thanallowable data rates which would be rejected by DSLAM 208.

For downstream flow 818 (from DSLAM 208 to MODEM 22), the line conditionmeasurements are typically made at MODEM 222. In some embodiments, theDSLAM 208 may formulate the new downstream rate values. In suchembodiments, the DSLAM 208 may send read downstream ATN/SNR requestmessages 810, and the MODEM 222 should respond with downstream noisereport (ATN/SNR) messages 812. In such embodiment, the DSLAM 208 willuse the information in messages 812 to calculate a new downstream datarate.

The DSLAM 208 assigns a new downstream data rate and conveys theinformation to MODEM 222 via message 814. MODEM 222 responds with anacknowledgement 816, and then downstream flow at the new assigned DSLdata rate 818 may be performed.

For upstream flow 824 (from MODEM 222 to DSLAM 208), the line conditionmeasurements, and rate adjustments checks and decisions are typicallyperformed at DSLAM 208. When DSLAM 208 decides that a new upstream rateshould be assigned, it conveys the information to MODEM 222 via message820, and MODEM 222 responds with an acknowledgement 822. Then upstreamsignal flow 824 at the new assigned DSL upstream date rate may beperformed.

FIG. 9 shows a table 900 describing some exemplary embedded operationschannel (EOC) messages which may be used to convey information utilizedin some implementation of the present invention. First column 914 liststhe HEX EOC Opcodes, while second column 916 describes the Opcodefunction. Third column 918 lists the direction of message flow(downstream and/or upstream). Fourth column 920 lists abbreviations usedfor each Opcode function described. First row 902 lists titles for eachcolumn of the table. The second row 904 lists the Request Test parameterUpdate (REQTPU) Opcode 13(H); the DSLAM 208 sends the REQTPU message tothe MODEM 222 in the downstream direction, e.g., during initialization,and the MODEM 222 acknowledges by sending a test parameter update in amessage to the DSLAM 208 in the upstream direction. The third row 906lists the Write data register numbers O-F (Write) commands and thesixteen corresponding Opcodes, each Opcode corresponding to one ofsixteen registers in MODEM 222. A Write Data command may be used, e.g.,to transfer downstream provisioned rate information from the DSLAM 208into a configuration register of MODEM 222, and MODEM 222 may respondwith an acknowledgement message. The fourth row 908 lists the Read dataregister numbers O-F (Read) commands and the sixteen correspondingOpcodes, each Opcode corresponding to one of sixteen registers in MODEM222. Read data command messages may be used, e.g., to request downstreamATN and SNR information from MODEM 222 by the DSLAM 208; MODEM 222 willrespond and return the contents of its line attenuation and SNR marginregisters. Fifth row 910, list the Write new Data Rate command (NewWrite) using Opcode 19, which may be used to convey new assigned datarates from DSLAM 208 to MODEM 222. Sixth row 912, lists an uplinkRequest new Data Rate (REQNDR) Opcode 1A, which may be used by MODEM 222to request new assigned data rates, either higher or lower, from DSLAM208. Other EOC messages are possible to accomplish the signaling inaccordance with the invention. Within the EOC message structure, thereare a number of undefined Opcodes which have been reserved for futureexpansion, and there are a number of Opcodes reserved for vendorproprietary protocols, as well as reserved and vendor discretionarymodem registers. Any of these reserved and/or vendor discretionaryOpcodes and/or registers may be utilized for the purposes ofimplementing the present invention.

While increasing a DSL line rate in response to detecting SNR conditionsabove a pre-selected increasing threshold has been described, in someembodiments before the line rate is increased, a test is made on theadditional frequencies which will be used to support the higher datarate. In such a case, since the frequencies being tested using a testsignal are different from those which are used to support an ongoingcommunications session at the lower rate, the test of the additionalfrequencies need not interfere with ongoing communications. In such acase, the test signal is used to determine if the additional frequencieswill support the higher data rate to which the line rate is going to beswitched. Assuming satisfactory test results at the additionalfrequencies, the transition to the higher data rate proceeds asdescribed above. However, if the testing of the previously unusedfrequencies indicates a problem, e.g., a higher than expected SNR forthe additional, previously unused frequencies which will be used tosupport the higher data rate, the transition to the higher data rate isnot made and the line rate is not altered until such time as both a SNRexceeding the increasing threshold is detected and a test of theadditional frequencies provides satisfactory test results.

1. A method of controlling at least one line rate corresponding tocommunication in a first direction over a line coupling a first digitalsubscriber line modem located in a central office and a second digitalsubscriber line modem located at a customer's premises together, themethod comprising: establishing a communications session includingcommunication in said first direction between said first modem and saidsecond modem at a first line rate as a function of a first signal noisemeasurement, said step of establishing a communications sessionincluding performing a synchronization operation to synchronizecommunication between said first modem and said second modem in saidfirst direction; making a second signal noise measurement; generating asa function of said second signal noise measurement, a second signalnoise measurement value; comparing said second signal noise measurementvalue to a first rate adjustment threshold; and changing said at leastone line rate as a function of the result of said comparison of saidsecond signal noise measurement value to said first rate adjustmentthreshold, when said second signal noise measurement value differs fromsaid first rate adjustment threshold in a pre-selected manner, withoutperforming a resynchronization operation.
 2. The method of claim 1,wherein said second signal noise measurement is a signal to noisemeasurement; and wherein said second signal noise measurement value is asignal to noise value.
 3. The method of claim 1, wherein said first rateadjustment threshold is a rate increasing threshold; and wherein saidstep of changing said at least one line rate as a function of the resultof said comparison includes: increasing said line rate when said secondsignal noise measurement value exceeds said first rate adjustmentthreshold.
 4. The method of claim 3, further comprising: comparing saidsecond signal noise measurement value to a second rate adjustmentthreshold; and changing said at least one line rate as a function of theresult of said comparison of said second signal noise measurement valueto said second rate adjustment threshold, when said second signal noisemeasurement values differs from said second rate adjustment threshold ina pre-selected manner, without performing a resynchronization operation.5. The method of claim 4, wherein said second rate adjustment thresholdis a rate decreasing threshold; and wherein said step of changing saidat least one line rate as a function of the result of said comparisonincludes: decreasing said line rate when said second signal noisemeasurement value is below said first rate adjustment threshold.
 6. Themethod of claim 1, wherein said first rate adjustment threshold is arate decreasing threshold; and wherein said step of changing said atleast one line rate as a function of the result of said comparisonincludes: decreasing said line rate when said second signal noisemeasurement value is below said first rate adjustment threshold.
 7. Themethod of claim 1, wherein said second modem makes said second signal tonoise measurement and performs said comparing operation, the methodfurther comprising: operating said second modem to transmit a requestfor a change in said line rate to said first modem; and operating saidfirst modem to send a command to said second modem to write a new linerate into a register included in said second modem.
 8. The method ofclaim 7, wherein said request for a change in said line rate and saidcommand are transmitted over said line using an embedded operationschannel.
 9. The method of claim 1, wherein said central office furtherincludes a provisioning system, the method further comprising: operatingsaid provisioning system to receive a request for a change in asubscriber line rate from a subscriber using said line; operating theprovisioning system to modify subscriber line rate information includedin said first modem; and operating the first modem to write a new linerate to said second modem while maintaining the establishedcommunications session and without performing a resynchronizationoperation.
 10. The method of claim 9, further comprising: transmittingsaid request for change in the subscriber line rate to said provisioningsystem over said line, said request being for a higher line rate than acurrent maximum permitted subscriber line rate.
 11. The method of claim10, further comprising: tracking the amount of time said subscriber'smaximum permitted line rate is set to the higher line rate; and billingthe subscriber based on the amount of time the subscriber's maximumpermitted line rate is set to the higher line rate.
 12. A communicationssystem, comprising: a digital subscriber line; a first modem located ata telephone central office coupled to a first end of said digitalsubscriber line; a customer modem located at a customer's premisescoupled to a second end of said digital subscriber line, the customermodem including: i) means for periodically monitoring the signal tonoise condition on said line during a communications session establishedbetween said first modem and said customer modem; ii) means forrequesting a change in line rate from said first modem in response todetecting a signal to noise condition which does not cause a loss insynchronization with said first modem but differs from a predeterminedthreshold in a preselected manner; said first modem including: i) meansfor establishing a communications session at an initial line ratedetermined as a function of a first signal noise measurement; and ii)means for generating a command to write a new line rate into saidcustomer modem in response to a request for a new line rate receivedfrom said customer modem without interfering with an establishedcommunications session between said first modem and said customer modemand without performing a resynchronization operation.
 13. The system ofclaim 12, wherein said customer modem includes memory for storing saidpredetermined threshold, said predetermined threshold being a rateincreasing threshold.
 14. The system of claim 12, wherein said customermodem includes memory for storing said predetermined threshold, saidpredetermined threshold being a rate decreasing threshold, said ratedecreasing threshold being a threshold signal to noise value which ishigher than a signal to noise value which results in loss ofsynchronization between said first modem and said customer modem. 15.The system of claim 13, wherein said customer modem includes means fortransmitting said request for a new line rate to said first modem overan embedded operations channel.